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Re: [Xen-devel] [PATCH v2] Fix scheduler crash after s3 resume

I think I had already raised the question of the placement of
this rcu_barrier() here, and the lack of a counterpart in the
suspend portion of the path. Keir? Or should
rcu_barrier_action() avoid calling process_pending_softirqs()
while still resuming, and instead call __do_softirq() with all but
RCU_SOFTIRQ masked (perhaps through a suitable wrapper,
or alternatively by open-coding its effect)?

Though I recall these vcpu_wake crashes happen also from other entry points in enter_state but rcu_barrier, so I dont think removing that helps much. Just was unable to get a proper log of them today due to most of them being cut in half. Will try bit more.

My belief is that as long as vcpu_migrate is not called in cpu_disable_scheduler, the vcpu->processor shall continue to point to offline cpu. Which will crash if the vcpu_wake is called for that vcpu. If vcpu_migrate is called, then vcpu_wake will still be called with some frequency but since vcpu->processor shall point to online cpu, and it won't crash. So likely avoiding the wakes here completely is not the goal, just the offline ones.

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